Mechanics (Mass, Motion, Force, Acceleration, Momentum, Work, Power, Energy)

Total Questions: 40

21. Static science is associated with - [M.P.PC.S. (PRE) 2012]

(a) Dynamic Situation
(b) Situation rest
(c) Mental Situation
(d) Data analyzing

Correct Answer: (b) Situation rest

Solution:Static is a branch of mechanics associated with the situation of rest.

22. Assertion (A) :A man standing on a completely frictional surface can propel himself by whistling. Assertion (B) :If no force act on system then momentum cannot change. [I.A.S. (PRE) 2000]

(a) both A and R are true and R is the correct explanation of A.
(b) both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Correct Answer: (b) both A and R are true but R is not the correct explanation of A.

Solution:First statement is explained on the basis of third law of motion, every action there is equal and opposite reaction. while whistling a man uses his breadth as a propellant to propel himself. If no force act on system then momentum cannot change. Hence the statement both A and R are true but R is not the correct explanation of A.

23. It is difficult to walk on the ice then on the road because : [U.P.P.C.S. (PRE) 1994]

(a) road is harder then the ice
(b) ice is harder then the road
(c) ice does not offer any reaction when we push it with our feet.
(d) Ice has lesser friction then the road.

Correct Answer: (d) Ice has lesser friction then the road.

Solution:It is difficult to walk on the ice then on the road because ice has a lesser friction then in the road.The toughness of the road surface,s gives you much friction force which enable us to move on the road.

24. Consider the following statement and conclusion which can be drawn from it. choose the correct conclusion, in starting a lorded cart one has to push harder then to keep it moving. [U.P.P.C.S. (mains ) 2013]

(a) the weight of a moving object is less
(b) the wheels tend to slip initially.
(c) there is less friction once the cart start moving
(d) practice makes perfect

Correct Answer: (c) there is less friction once the cart start moving

Solution:Once you start the object moving the friction decreases from the static friction holding the object in place. you have seen this in trying to slide a heavy box across the floor.it may be very difficult to move but once it start sliding it is easier to move. Because sliding and rolling friction is less than static friction.

25. A goalkeeper in game of football pulls his hands backwards while holding the ball shot at goal.This enable to goalkeeper to : [68th B.P.S.C. (PRE) 2022]

(a) decrease the rate of change of momentum.
(b) exert large force on the ball.
(c) increase the force exerted by the ball on the hands.
(d) none of the above.

Correct Answer: (a) decrease the rate of change of momentum.

Solution:According the newton second law of motion
F=M×A
OR

F=m(v-u)/t
so by pulling his hands the goalkeeper increase the time to hold the ball. By increasing the time he decreases the force applied by the ball on him.

26. For every action there is equal an opposite reaction is given by ; [U.P.R.O/A.R.O.(MAINS)2017]

(a) Newton
(b) Albert Einstein
(c) Bohr
(d) Handane

Correct Answer: (a) Newton

Solution:For every action there is equal an opposite reaction known as the third law of motion. That statement means that in every interaction there is pair of force acting on the body or object. The amount of the force on the first object is equal to amount of the force on the other object. The direction of the force is opposite to each other.

27. Centripetal force is responsible to : [68th B.P.S.C. (PRE)2022]

(a) independent motion of the object in space.
(b) keep the body moving in the circular path.
(c) fly the object along a straight line.
(d) none of the above.

Correct Answer: (b) keep the body moving in the circular path.

Solution:Centripetal force means the Centre seeking force otherwise things would just travel in a straight line rather then circular. So centripetal force is used to refer the force acting on a circular path. For example the Earth rotates around the sun in circular motion, any satellite circular motion in any celestial body. The force causing the motion is the result of the gravitational attraction between them.

28. An effective coriolis force results from : [67th B.P.S.C. (PRE)2022]

(a) solar system
(b) earth rotation
(c) interior of the earth
(d) colorado and gulf stream

Correct Answer: (b) earth rotation

Solution:In physics the coriolis force is an inertial or fictitious force that acts on objects in motion within the frame of reference that rotate with respect to an inertial frame. This force causes moving objects on the surface of the earth to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere.

29. A man jumped at a speed of 5 meter per second from a stationery boat moved off with the speed of 0.5 meters per second .How many times is the mass of the boat greater than that of the man: [I.A.S. (PRE) 1994]

(a) 2.5 times
(b) 5.5 times
(c) 4.5 times
(d) 10 times

Correct Answer: (d) 10 times

Solution:Let the mass of the person is M and the mass of the boat is N then,

momentum of the boat + momentum of the person before jump=0

Then the momentum of both after mans jump = M5-N×0.5=0 {According to the principal of conservation of momentum }

∴ N×0.5=M×5 ⇒ N/M=5/0.5=10

Thus the mass of the boat is 10 times greater then the mass of the man.

30. A truck a car and a motorcycle have a equal kinetic energy. If equal stopping forces are applied and they stop after travelling distance of X,Y AND Z respectively, then- [I.A.S.(PRE)1996]

(a) X >Y >Z
(b) X<Y<Z
(c) X=Y=Z
(d) X≅Y≅Z

Correct Answer: (c) X=Y=Z

Solution:If the object have kinetic energy and if equal forces stopping force applied on them then they would stop at the same distance .hence X=Y=Z.

« Previous 1 234 Next »